Continuous shrouding-riveted construction

ABSTRACT

A CIRCULAR SHROUDED ROTOR BLADE STRUCTURE FOR AN ELASTIC FLUID AXIAL FLOW TURBINE OR COMPRESSOR COMPRISING AN ANNULAR ROW OF BLADES AND AN ANNULAR SERIES OF ARCUATE SEGMENST ASSOCIATED WITH THE BLADES AND ARRANGED IN END-TOEND RELATIONSHIP TO FORM A CONTINUOUS 360* SHROUD, WHEREIN EACH PAIR OF NEIGHBORING SHROUD SEGMENTS IS FIRMLY RIV-   ETED TO A BLADE COMMON TO BOTH WITH EACH SEGMENT BEING RIVETED TO AT LEAST TWO BLADES. THERE MAY BE MORE THAN ONE ROW OF ARCUATE SEGMENTS FORMING THE SHROUD.

Nov. 7, 191 f R. J. ORTOLANO 3,102,221

CONTINUOUS SHROUNDING-RIVETED CONSTRUCTION Original Filed Sept. 30, 1969T I8 2o l8b 18a 11 r l8c |4 I lie l3 Hb H I u FIG.6.

IO 6 NVE TOR ROI h J o 1 T 1 p I OOnO M ATTORNEY United States Patent O3,702,221 CONTINUOUS SHROUDING-RIVETED CONSTRUCTION Ralph J. Ortolano,Palos Verdes Peninsula, Calif., assignor to Westinghouse ElectricCorporation, Pittsburgh, Pa. Original application Sept. 30, 1969, Ser.No. 862,282. Divided and this application June 15, 1971, Ser.

Int. Cl. F01d /22 US. Cl. 416-191 3 Claims ABSTRACT OF THE DISCLOSURE Acircular shrouded rotor blade structure for an elastic fluid axial flowturbine or compressor comprising an annular row of blades and an annularseries of arcuate segments associated with the blades and arranged inend-toend relationship to form a continuous 360 shroud, wherein eachpair of neighboring shroud segments is firmly riveted to a blade commonto both with each segment being riveted to at least two blades. Theremay be more than one row of arcuate segments forming the shroud.

BACKGROUND OF THE INVENTION This is a division of application Ser. No.862,282 filed Sept. 30, 1969, now Pat. No. 3,606,578.

This invention relates, generally, to an elastic fluid axial flowturbine or compressor and, more particularly, to a shrouded rotor bladestructure.

The primary advantage of providing shrouding on the tips of rotor bladesis to minimize vibrational forces, thereby minimizing vibrationalstresses in the blades, as well known in the art. The shrouding,however, may subject the blades to additional thermal bending stresses.

Turbine blades which are fastened to the same shroud segment haveseveral different material vibrational modes. The tangential modevibration is the in-phase vibration in the plane of maximum flexibility,perpendicular to the rotational axis of the rotor. The axial modevibration is the in-phase vibration in the direction of the axis.

The invention minimizes the tangential and axial vibrational modes andminimizes the thermal bending stresses. Furthermore, this rotor bladestructure is inexpensive to manufacture and can be easily andeconomically repaired.

Earlier inventions of this type are disclosed in A. J. Partington Pat.3,367,629 and P. D. Saunders patent 3,367,630 both issued on Feb. 6-,1968 and both assigned to the same assignee as this invention.

SUMMARY This invention relates, generally, to a elastic fluid axial flowturbine or compressor and, more particularly to a shrouded rotor bladestructure.

The structure comprises an annular row of blades and an annular seriesof arcuate segments arranged in end-toend relationship to form acontinuous 360 shroud. Each pair of neighboring segments is connected toa blade common to both and each segment is connected to at least twoblades. There may be more than one row of segments forming the shroudand there may be more than one layer of shroud segments.

Four embodiments are illustrated in the drawings. The first embodimentcomprises a single row of segments of parallelogram shape in plan whereeach segment is riveted to two blades and each pair of neighboringsegments is riveted to a blade common to both. The second embodiment issimilar to the first except the shroud segment is riveted to more thantwo blades and at least one blade is solely riveted to the shroudsegment. The third embodi- 3,702,221 Patented Nov. 7, 1972 ment issimilar to the first embodiment except that there are two rows ofsegments in side-by-side relationship and each blade is riveted to aside-by-side segment with one rivet in each row. The fourth embodimentis similar to the first except that the outermost tip of the blade isarcuately shaped and conforms to the arcuate shroud segment.

Elastic fluid flows through the turbine at high temperature andpressure, turning the rotor. As the shroud expands due to thecentrifugal and thermal forces, the segments rotate slightly around therivets so that the segments are in sliding, frictional abutment withtheir adjacent segments creating frictional damping and thus minimizingthe stresses due to the centrifugal forces and the thermal strains.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a partial section of a rotorwith a shrouded blade structure in elevation formed in accordance withthe present invention;

FIG. 2 is a developed view, on a larger scale, of the shroud structuretaken along line II-II of FIG. 1 showing a plan view of the shroud;

FIG. 3 is a view on the same scale as FIG. 2, partly in elevation andpartly in section, taken along line IIIIII in FIG. 1;

FIG. 4 is a view similar to FIG. 2, but showing another embodiment ofthe invention;

FIG. 5 is a view similar to FIG. 2, but showing a further embodiment ofthe invention;

FIG. 6 is a fragmentary view taken along line VIVI in FIG. 5; and

FIG. 7 is a fragmentary view in perspective of a still furthermodification of the shroud.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to the drawings indetail and particularly to FIG. 1, there is shown a portion of a rotor10 having a transverse annular row of blades 11 substantially identicalto each other and further identified by alphabetical suf fixes 11a, 11b,110, etc. signifying their relationship to each other, and a shroud 12,surrounding the outermost tips of the blades 11. As indicated in FIG. 2,the blades 11 are of the usual airfoil contour as well known in the artwith a leading edge 13 and a trailing edge 14.

As shown more clearly in FIG. 3, the blades 11 are provided withsuitable root portions 16 which are disposed in a suitable peripheralgroove in the rotor 10. The blades '11 extend radially outward relativeto the axis of rotation of the rotor 10' indicated by the dot-dash lineRR, and they may constitute one stage of a multi-stage axial flowturbine (not shown). 0n the radially outermost tip portion of the blade11 are two tenons 20, which, as illustrated, are integral with theblade.

The shroud 12 comprises an annular series or arcuate segments 18substantially identical to each other and further identified byalphabetical sufiixes 18a, 18b, 180, etc. signifying their end-to-endrelation to each other. The segments 18 form a continuous 360 shroud.Referring to FIG. 2, the segment 18a is securely connected to the twoblades 11a, 11b by the tenons 20. In a similar manner, segments 18b issecurely fastened to the two blades 11b and 11c by the tenons 20 andsegment 18c is securely fastened to the two blades 11c and 11d. Theremaining segments proceed in the manner described above.

As shown in FIG. 2, the segment 18b is a segment of an arc and is ofparallelogram shape in plan and the end portion 19 of the segment 18blies in a plane which forms an oblique angle (1) with the axis ofrotation of the rotor RR. The segment 18b has two apertures throughwhich the tenons 20 projects. A line connecting the adjacent tenon onthe leading edge 13 of the blade 11b and the tenon on the trailing edge14 of the blade 11c lies in a plane which forms an actute angle with theaxis of rotation of the rotor. The tenons 20 are deformed such as byriveting to tightly connect the segment 18b to the blades 11b and 110. Asimilar analysis can be made for the remaining segments, blades andtenons.

The neighboring segments 18a and 18b are riveted to the blade 11b commonto both segments and correspondingly, the remaining segments arefastened in a similar arrangement.

The tenons are arranged in two circular rows indicated by the dot-dashlines AA, B-B conforming to the curvature of the shroud 12, and whichrows lie in planes perpendicular to the axis of rotation of the rotorR-R.

The shroud 12 comprises a single layer and a single row of segments 18.

As previously explained, as the shroud segments 18 expand and theadjacent segments 18a and 18b tend to frictionally engage each other,the stresses build up in the segments, but no frictional damping occursunless the segments slide on each other. The blade 11b is connected byone tenon 20, to segment 18a, and by a second tenon 20, to the adjacentsegment 18b. As the stresses continue to increase, the segment 18bminutely pivots or rotates around the tenon 20 causing a'slight movementalong the edge portion 19 of the segments 18a and 180. There will be acorresponding movement of the segments 18a and 18c along the endportions 19 of the segment 18b so that the segments frictionally slidealong the adjacent end portions 19 and produce frictional damping bydissipating the stresses and minimizing thermal distortion. A similaranalysis can be made for the remaining segments which cooperate witheach other in a like manner.

DESCRIPTION OF THE SECOND EMBODIMENT The second embodiment, as shown inFIG. 4, is similar to the shrouded rotor blade structure in FIGS. 1, 2and 3 but differs in the following manners. The shroud 24 comprises anannular series of arcuate segments 21 substantially identical to eachother and further identified by alphabetical suffixes 21a, 21b, etc.characterizing their end-to-end relationship with each other. The shroudsegment 21b is firmly connected to more than two blades for example,blades 22a, 22b, 22c and 22d. Each pair of neighboring segments 21a and21b is firmly connected to the blade 22a common to both and theremaining blades 22b and 220 are entirely connected to the shroudsegment 21b. A similar analysis can be made for the remaining segments.

The primary advantage of this embodiment is economy; the fewer thenumber of shroud segments to manufacture and assemble, the lessexpensive it is to produce the rotor structure. However, as the numberof segments 21 approaches the lower limit of two segments, in which allthe blades 22 except for two are entirely connected to the shroudsegments, frictional damping is virtually eliminated and there is acorresponding increase in thermal distortion. On the other hand, as thenumber of shroud segments increases, approaching the configuration ofthe first embodiment 12, where each segment 18 is connected to only twoblades, there is a corresponding increase in frictional damping and areduction of thermal distortion.

DESCRIPTION OF THE THIRD EMBODIMENT The third embodiment shown in FIGS.5 and 6 is substantially similar to the first embodiment but differs inthe following. The shroud 28 comprises a left row 32 of segments 25a,25b, 250, etc. and a right row 33 of segments 27a, 27b, 27c, etc. whichare substantially the same size and shape, the alphabetical suffixescharacterizing their end-to-end relationship with each other. The rows32, 33 are arranged in side-by-side relation with each other and thesegments 25a and 27a, 25b and 27b, 25c

and 27c, etc. are staggered relative to each other. There are two tenons30 integral with the blade 29a and each tenon is connected to aside-by-side segment 25 and 27a with one tenon in each row 32, 33.Similarly, two tenons 30 are integral with the blade 29b and each tenonis connected to a side-by-side segment 25a and 27b with one tenon ineach row 32, 33. Each pair of adjacent blades 29a and 29b joins threesegments 25a, 27a and 27b with one segment 25a common to two blades 29aand 2911. A similar relationship exists among segments 25b and 270,blades 29c, and 29, and tenons 30 and the remaining segments, blades,and tenons.

The advantage of this embodiment is that any motion will produceadditional frictional damping because of the increased area of contactbetween the segments 25a and 27a, 25b and 27b, and the cooperatingremaining segments of the shroud 28.

DESCRIPTION OF THE FOURTH EMBODIMENT The fourth embodiment shown in FIG.7 is substantially similar to the first embodiment except for thedifferences which follow. The outer shroud 40 comprises an annularseries of arcuate segments 34 substantially identical to each other andfurther identified by alphabetical suifixes 34a, 34b, etc.characterizing their end-to-end relationship with each other. Thesegments 34 are similar in size and shape and, as illustrated, are ofparallelogram shape in plan.

Each blade 36 has an outermost tip forming an integral blade cover 38 ofarcuate segmental shape substantially identical to each other andfurther identified by alphabetical sufiixes 38a, 38b, etc. indicatingtheir end-to-end relationship. The blade covers 38, 38a, 38b, etc. forma continuous 360 inner shroud 37 which shroud conforms to and cooperateswith the outer shroud 40. As indicated, the arcuate segments or bladecovers 38 are rectangular in plan.

Two tenons 39 are integral with and extend radially outwardly from theblade cover 38 and the shroud segments 34 and 34b are fastened to theblade cover 38 by deformation of the tenons 39 as previously described.Similarly, two tenons 39 are integral with the blade cover 38a and theshroud segments 34a and 34b are fastened in a like manner to the bladecover 38a. A similar analysis can be made for the remaining segments.

The segments 34 of the outer shroud 40 are disposed in staggeredrelation on the blade covers 38 of the inner shroud 37. The edge portion41 of the segment 34a forms an oblique angle a with the edge portion 42of the blade cover 38a and a similar relation exists among the remainingedge portions. In this manner, better sealing against leakage of motivefluid by the shroud is obtained since there is no direct opening throughthe two shrouds. Another advantage to this embodiment is that the innershroud 37 offers better tip contour whereby better fastenmg to the outershroud 40 from the blades 36 can be secured.

Although more than one embodiment has been shown, 1t .18 intended thatall the matter contained in the foregoing description or shown in theaccompanying drawing shall be interpreted as illustrative and not in thelimiting sense.

What is claimed is:

1. In elastic fluid utilizing apparatus,

a rotor having a transverse annular row of blades,

a continuous shroud surrounding the radially outermost tips of theblades,

said shroud comprising an annular series of outer arcuate segmentsarranged in end-to-end relationship with each other,

means connecting each segment securely to at least two blades,

each pair of neighboring segments being firmly connected to a bladecommon to both,

each of said blades having an outermost tip and said tips forming aninner shroud structure which conforms to the arcuate shroud segments,said inner shroud structure comprising an annular series of arcuatesegments which are rectangular in plan, and said outer shroud segmentsare parallelograms in plan and these segments have end portions whichare slanted relative to the axis of rotation of the rotor. 2. Thestructure recited in claim 1 wherein the inner shrouds are disposed inabutment with each other and the outer shrouds are disposed in abutmentwith each other.

3. The structure defined in claim 1 wherein the segments of the outershroud are disposed in staggered relation on the segments of the innershroud and the end portions of the outer segments form oblique angleswith the end portions of the inner shroud segments.

References Cited UNITED STATES PATENTS EVERETTE A. POWELL, JR., PrimaryExaminer US Cl. X.R.

